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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

S04                                ALASKAN GLACIER STUDIES
cascading glaciers, therefore, Vassar Glacier is the least attractive, because the whole of its lower surface is dark and moraine-covered. On both the north and south sides, streams emerge from the ice about a half mile back from the terminus and flow near the ice edge, building an alluvial fan on each side.
The tidal terminus of Vassar Glacier is not a perpendicular white cliff of clean ice, as in the other tidal cascading glaciers, but a low sloping margin, mantled with rock debris, and similar to the terminus of the Malaspina Glacier at Sitkagi Bluffs. As a result of a slight advance which was in progress in 1910, a part of the northern portion of the glacier was acquiring a more precipitous cliff and was shedding the debris mantle, so that the ice was revealed in places. Even here, however, in contrast with the glistening white cliffs of the adjacent glaciers, the ice in sight was dirty and marked with wavy horizontal lines of englacial material. Few, if any, icebergs are discharged from this glacier.
Gilbert describes Vassar Glacier in 1899 as a cascading glacier "parallel to the Smith and Bryn Mawr and exhibiting a similar series of cascades, but of smaller size and less direct in its course. It is cumbered, especially in its lower part, by rock debris, and close inspection was necessary to determine the fact that it is actually tidal."
It was, therefore, not essentially different in 1899 and 1910, and photographs by Grant show this to have been the case also in 1905 and 1909. It is not smaller than the Smith Glacier, though it is smaller than Bryn Mawr. The establishment of the facts of the debris-covered lower end and the barely tidal condition in 1899 are of importance, for these remained the same until 1910 when a change was commencing. At the time of our visit the glacier touched tidewater along the whole portion of the front between the flanking alluvial fans, but with a low, sloping moraine-veneered margin along the southern half, and with a low, dirty, nearly vertical cliff in the northern half (PL CXIX).
Photographs show that there were barren zones on each side of the glacier in the cascading portion in 1899. There was sufficient advance of Vassar Glacier before 1910 so that portions of the barren zones were covered. That on the north side near sea level was not completely overridden by July 21,1910, but higher on the fiord wall it was almost covered. A great deal of the barren zone on the south side was still visible except in the bulb portion near sea level.
Qn the northern margin the glacier was advancing, but there was no thrusting forward of the ice itself, the advance being manifested chiefly by a slight folding, ridging, and crumpling in the moraine-covered hill along the northern margin, whose barren condition suggests that it contains a buried ice block.
The southern edge of the glacier at sea level was also obviously advancing, but no ice was seen beneath the ablation moraine cover and the advance was manifesting itself principally by the commencement of crevassing in the moraine-covered bulb and by the sliding down of this morainic material along the glacier margin, where willows and alders were being buried. Near sea level the glacier extended right up to the forest which included mature spruces.
High above sea level, the ice edge had advanced over part of the zone of bare rock that had existed there since 1899, but it was not all covered. Ice blocks were sliding down and accumulating in a talus at one point, suggesting that the advance was still in progress.
Vassar Glacier had been stagnant and motionless long enough, not only for thinning